1. Field of the Invention
The present invention relates to liquid crystal display, and more particularly, to a method and apparatus for driving a liquid crystal display panel that is capable of driving a liquid crystal display panel having five color dots within one pixel as well as reducing flicker.
2. Discussion of the Related Art
Generally, a liquid crystal display (LCD) controls a light transmittance of each liquid crystal cell in accordance with a video signal to thereby display a picture. An active matrix LCD including a switching device for each liquid crystal cell is suitable for displaying a dynamic image. The active matrix LCD uses thin film transistors (TFT's) as switching devices.
FIG. 1 is a block diagram of a typical liquid crystal display driving apparatus.
Referring to FIG. 1, the LCD driving apparatus includes a digital video card 1 for converting analog video data into digital video data, a data driver 3 for applying the digital video data to data lines DL of a liquid crystal display panel 6, a gate driver 5 for sequentially driving gate lines GL of the liquid crystal display panel 6, and a timing controller 2 for controlling the data driver 3 and the gate driver 5.
The liquid crystal display panel 6 has a liquid crystal injected between two glass substrates, on which the gate lines GL and the data lines DL cross each other perpendicularly. Each intersection between the gate lines GL and the data lines DL is provided with a thin film transistor (TFT) for selectively applying an image inputted from each data line DL to a liquid crystal cell Clc. To this end, the TFT has a gate terminal connected to the gate line GL, a source terminal connected to the data line DL and a drain terminal connected to a pixel electrode of the liquid crystal cell Clc.
The digital video card 1 converts an input analog image signal into a digital image signal suitable for the liquid crystal display panel 6, and detects a synchronizing signal included in the image signal.
The timing controller 2 supplies red(R), green(G) and blue(B) digital video data from the digital video card 1 to the data driver 3. Further, the timing controller 2 generates data and gate control signals such as a dot clock Dclk and a gate start pulse Gsp using horizontal and vertical synchronizing signals H and V inputted from the digital video card 1 to make a timing control of the data driver 3 and the gate driver 5. The data control signal such as a dot clock Dclk is applied to the data driver while the gate control signal such as a gate start pulse Gsp is applied to the gate driver.
The gate driver 5 includes a shift register (not shown) for sequentially applying a scanning pulse in response to the gate start pulse Gsp from the timing controller 2, and a level shifter. (not shown) for shifting a voltage level of the scanning pulse into a level suitable for driving the liquid crystal cell Clc. The TFT applies a video data on the data line DL to the pixel electrode of the liquid crystal cell Clc in response to the scanning pulse from the gate driver 5.
The data driver 3 receives R, G and B digital video data along with a dot clock Dclk from the timing controller 2. The data driver 3 latches the R, G and B video data in synchronization with the dot clock Dclk and then corrects the latched data in accordance with a gamma voltage Vγ. Furthermore, the data driver 3 converts data corrected by the gamma voltage Vγ into analog data to apply them to the data line DL one line by one line.
FIG. 2 represents a relationship between a pixel and a TFT structure of the LCD shown in FIG. 1.
Referring to FIG. 2, the pixel of the LCD consists of an area defined by four data lines DL1 to DL4 and two gate lines GL1 and GL2. A pixel electrode 12a is provided at an area surrounded by the gate lines GL1 and GL2 and the data lines DL1 and DL2, forming one pixel. A pixel electrode 12b is provided at an area surrounded by the gate lines GL1 and GL2 and the data lines DL2 and DL3. A pixel electrode 12c is provided at an area surrounded by the gate lines GL1 and GL2 and the data lines DL3 and DL4 which makes one pixel. One picture element 16 consists of these three pixels, and a side of each pixel electrode 12 is provided with a TFT 14 which is a switching device.
Typically, color filters R, G and B are provided at the substrate opposite the transparent substrate with the pixel electrode. In this case, an R color filter is arranged at a position corresponding to the left pixel electrode 12a of one picture element shown in FIG. 2; a G color filter is arranged at a position corresponding to the middle pixel electrode 12b; and a B color filter is arranged at a position corresponding to the right pixel electrode 12c. 
For a VGA resolution display, 640 data lines DL and 480 gate lines GL are provided resulting in 307200 picture elements.
FIG. 3 shows an arrangement of the R, G and B color filters and a connection between the gate driver 5 and the data driver 3 in the conventional LCD of FIG. 1. Referring to FIG. 3, the data driver 3 receives input signals Re (Red even), Ge (Green even), Be (Blue even), Ro (Red odd), Go (Green odd) and Bo (Blue odd) of a six-bus system and outputs them to the 1st to nth data lines DL1 to DLn in synchronization with a data clock.
The R signal is output to the first data line DL1 via the data driver 3; the G signal is output to the second data line DL2 via the data driver 3; and the B signal is output to the third data line DL3 via the data driver 3. The three output signals make a pair repetitively. At this time, depending on a line arrangement through the data driver 3, the B signal is output to the first data line DL1 via the data driver 3; the G signal is output to the second data line Dl2 via the data driver 3; and the R signal is output to the third data line DL3 via the data driver 3.
The LCD adopts a dot inversion driving system as shown in FIG. 4A and FIG. 4B. In the dot inversion system as shown in FIG. 4A and FIG. 4B, data signals of opposite polarities are applied to liquid crystal cells adjacent to each other for each column line and each row line on the liquid crystal display panel. The polarities of data signals applied to all liquid crystal cells of the liquid crystal display panel are inverted every frame. In other words, when video signals at a certain frame is displayed, data signals are applied to the liquid crystal cells of the liquid crystal display panel such that they have alternating positive polarity (+) and negative polarity (−) as the liquid crystal cells go from the left side to the right side in a row and from the top to the bottom in a column, as shown in FIG. 4A. Subsequently, for the next frame, the polarity of the data signals applied to the liquid crystal cells are inverted to be opposite to the polarity in the previous frame, as shown in FIG. 4B.
The conventional method of driving the liquid crystal display panel having such stripe-type pixels has a limit in improving picture quality, and has a problem in that it causes a flicker phenomenon upon driving the liquid crystal display panel by the dot inversion system.